Chevy - Piston Slap?

Question

Been trying to figure out what this knocking/ticking noise is.

01 Chevy Malibu 3100

Worse when cold - and has been getting worse recently.

Thought it could be a rocker arm or pushrod but they seemed to be fine (Im replacing 2 rods because they had some wear - 1 could be slightly warped - doesnt seem like enough damage for the level of noise). Another guy said it could be the intake gasket since the 3100 with dexcool have a problem with that (was some nasty coolant sludge inside)

Then someone brings up a piston slap - which I really had no idea but when I looked it up it sounded like that could be it???

Basically I dont know how to rebuild an engine and Im not paying for it to be done... so after I put the new rods and gasket in and put all the sh*t back together if the noise is still there I will try the spark plug trick to see what cylinder it is.... but beyond that what can I do - would thicker oil help at all? Or is this likely not the problem?

Also the noise gets louder as I accelerate.

Answer 1

Connecting rod. motor get wet? anyway. rebuild or replace. big money,

Answer 2

Oh man! You just needed a little help in measuring the bores and the piston skirts when you had it apart. The problem was you didn't have enough informed information. It takes a minimum of a telescoping gage to snap inside the bore and an outside micrometer to measure the outside of the telescoping gage after carefully pulling it out of the bore. You measure pistons at right angles to the piston wrist pins half way down the piston skirt. Subtract the skirt diameter from the thrust side of the bore. The clearance should be no more than .003 with the stock cast pistons. You may find by sorting a batch of stock pistons a few with skirts that will give you the proper clearance. If not I'm quite certain GM make oversize pistons in very small diameter changes. .002 -.005 to be exact.

I've actually whitnessed a Chevrolet dealer honeing a bore to fit very small oversizes in the past with the crankshaft still in place. Ouch! That's not the way I'd do it but it's a cheap fast fix.  

Answer 3

the 3.1 was noted for piston slap in the older ones and GM had recalls on them back then, I had a 94 grand am with the 3.1 that had the slap but it would go away once the car warmed up.

Answer 4

sounds like the valves are loose...or you have a bad compression gap